Drawing instrument



Aug. 3 1926.

m R s. 5 Mr H E W CHRISTY DRAWING INSTRUMENT Filed August 17, 1925 Patented Aug. 3, 1926.

U-NlTED STATES PATENT OFFICE.

' ELMER diameter, or CINCINNATI, OHIO.

DRAWING INSTRUMENT.

A ncamwfiiea 'Augusr17Q1e25. Serial No. 5 ,589.

An objectot my invention is to provide a drawing instrument which is particularly adapted to usein laying out drawingsupon a vertical blackboard, drawing board or the like.

Anotherobject is'to provide a device for thepurpose stated, bymeans of which may be drawn lines in perpendicular andhorizontal planes and at various angles thereto. Another objectis'to providea device of this 11inch whichi though not primarily in tended as a precision drawing instrument, is neverthelessvery accurate in that all lines drawn ttherebyare taken from an absolute perpendicular and 'tothisend, errors made work of greater accuracy than iso'rdinar'ily possible 'with devices of this kind."

These and otherobiects are attained by the means described hereimand in'the accompanying d'rawings,' in which Figil isa plan view of the device of my invention in position for drawing a horizontal line;

Fig; 2 is a-sim'ilar view showing the device in position for drawing aline at'an angl'e'to ahorizontalf Fig. 3 is a similar view showing the device in position for drawing a vertical line.

Fig. i is a tragmental cross-sectional view taken on line 4-4 of Fig. 1.

Fig. 5 is an end elevation of the device as shown in Fig. 1.

Fig. 6 is a cross-sectional view taken on line 6-6 of Fig. i.

The device of my invention comprises an integral scale, straight edge and protractor, which are provided with a rigid handle member mounted midway of the ends of the straight edge. A slotted indicator arm is freely pivoted beneath the handle member and is provided with an indicating point so that the pivotal mounting of the indicator and the indicator point thereof will always lie in a true vertical plane when the device is held against a perpendicular surface, such as a blackboard or the like. The straight edge 10 is provided with suitable graduations 11, which are numbered from zero at the longitudinal center 12 thereof and ex tend to the ends 18 and 14; An integral protractor body 15 has its radial-center in alignment with the zero point of the straight edge and the'90-degree line '16 of the .protra'ctor lies parallel with theworking edge of the straight edge 10. The protrac--; tor portion '15 is provided with suitable graduations'whi'ch may be numbered from zero at the centralportionrthereof'up to '90; degrees at theiine 16: At: the intersection of line '16'and a line extending through the zero markings straight edge isprovideda bore '18 andan enlarged concentric counter-bore 1.9"eittending from therear face of the'protractor. A shouldered. threaded nut- 21isadapted'to seat in the bore 18 and counter-bore 19 and to 'lieflush with 'tl'iereartace 20 of the device. A stud-22 is provided with threads'fla and threads 24 at its opposite ends. Threads 23 are received by a threaded nut 21 therebyserving to secure the stud'22 per pendicularly to the face of theprotractor;

A washer 241 spaces the shoulder of stud 22 from'the protractor. An arm 25 is pro vided with an elongated slot 26, lnto'one end otwhich extends asharp pro ection which serves as an indicator point 27; The end 28 of the arm 25 is providedwith a bore 29 adapted to receive an enlarged shoulder portion 3O on' the stud 22; The shoulder portion-3O ot the stud is'of a slightly-greater dimension than the thickness of the arm 25 so that an end-bearing washer 31 of handle will not bind on the arm 25. The handle 32 may be counter-bored as at 33 for re ceiving a suitable fastening nut 3 which engages the screw threads and the stud 22.

By reference to Fig. 4i it will be apparent that the stud 22 serves both as a securing means for the handle and as a bearing means for the arm 25. The lower end 35 is relatively heavier than the end 28 thereof and is so weighted that the arm will serve as a plumb with the point27 always indicating an absolute perpendicular. The elongated opening 26 enables the operator of the device to read the graduations on the protractor and enables him to bring the indicating point 27 and graduations 17 into registry.

The operation of the device is obvious. One using the combined protractor and straight edge would grasp the mstrument by onf the protractor and handle 32 and place it against a blackboard or vertical drawing board; should he desire to draw a horizontal line he would turn the device until the indicating point 27 registered with zero on the protractor, whereupon the straight edge 10 would lie in a plane 90 degrees to actual perpendicular. He would then draw a line of a desired length, using the graduations 11 for this purpose. .Should he then desire to erect a perpendicular to the horizontal line the device would then be turned by the handle 32 until the indicator point 27 registered with the line 16, whereupon he would be able to draw the line in a true perpendicular plane which wouldincidentally be at 90 degrees to the horizontal line previously drawn. In the same manner all lines drawn at intermediate angles would have their measurements taken with a true perpendicular as a starting point, so'that in the construction of various geometrical fig ures there would be eliminated the usual multiplication of errors and inaccuracies, which follows the drawing of a line at an angle to a given drawn line and then using the one end secured thereto, a weighted arm ro-- tatably mounted at one end on the stud and having indicating means at its other end for registry with the graduations on the protractor body, a handle on the free end of the stud and arranged to preclude separation of the arm from the stud and to preclude binding of the arm between the handle and body.

2. In a device of the class described the combination with a body member comprising anelongated graduated straight edge and an dle member to the stud in abutment with the shoulder portion thereof and an arm having a bearing bore at its one end for mounting the arm upon the shoulder portion ofthe stud, said arm having an elongated aperture at its opposite end and an indicating point disposed at one end of the elongated aperture for registering with the graduations on the protractor as the arm is moved on its pivotal mounting.

3. In an instrument of the class-described the combination of a body comprising a straight edge and a protract0r, a stud eX- tending from the body perpendicular thereto at the radial center of the protractor, an arm provided with indicating means adapted to register with the graduations on the protractor and at one end loosely receiving the stud whereby to permit free movement of the weighted arm about the stud, and handle means carried by the stud for manipulating the body relative to the Weighted arm.

In testimony whereof, I have hereunto subscribed my name this 8th day of August,

ELMER W. CHRISTY. 

